All-optical intensity modulation device

Abstract

The invention discloses an all-optical intensity modulation device, and belongs to the technical field of integrated photonics and all-optical signal processing. The all-optical intensity modulation device is integrally constructed on the same photonic integrated chip and is integrally packaged in a sealing cavity, and the sealing cavity is filled with absorptive gas; comprising an optical coupler used for combining signal light and pump light and guiding the signal light and the pump light to an input coupling end of a micro-ring resonator; the micro-ring resonator is used for enhancing the power of the pump light, modulating the output intensity of the signal light through the position change of a resonance peak to obtain modulated signal light, and exporting the modulated signal light through an output coupling end, the position change of the resonance peak is caused by heat energy generated by the pump light after the absorption power of the absorptive gas is enhanced, and the filter is used for filtering the modulated signal light. The filter is used for filtering residual pump light in modulated signal light. Through the combination of the gas photothermal effect and the micro-ring resonator, the intensity change of the pump light is converted into the intensity modulation of the signal light.

Description

Technical Field

[0001] This application belongs to the field of integrated photonics and all-optical signal processing technology, and specifically relates to an all-optical intensity modulation device. Background Technology

[0002] With the development of sensing technology, all-optical modulators are the core devices for realizing high-speed, low-power optical interconnects and optical computing in the fields of integrated photonics and all-optical signal processing. Traditional electro-optic modulation or all-optical modulation schemes based on semiconductor carrier effects often face challenges such as high power consumption, limited modulation depth, or high integration complexity with CMOS processes.

[0003] In recent years, all-optical modulation based on the gas photothermal effect has attracted attention as an emerging approach. It utilizes the absorption of pump light energy by an absorbing gas to generate localized temperature rises and refractive index changes, thereby achieving lossless, broadband phase modulation. However, existing technologies are mostly concentrated on non-planar structures such as micro / nano fibers, making it difficult to achieve high-density, large-scale integration with on-chip photonic circuits. Furthermore, these approaches primarily generate phase modulation, while practical systems often require more direct and easily detectable intensity modulation signals, limiting their direct application. Existing solutions typically require the additional introduction of interference structures such as Mach-Zehnder interferometers (MZIs) to complete the phase-to-intensity conversion. This not only increases device size and complexity but also imposes extremely stringent requirements on the system's phase stability, severely restricting the application prospects of this technology in practical integrated photonic chips.

[0004] Therefore, developing a highly efficient, compact, and on-chip integrated all-optical modulator has become a key bottleneck in promoting the application of this cutting-edge technology. Summary of the Invention

[0005] To address the aforementioned issues, this application provides an on-chip all-optical intensity modulation device based on the gas photothermal effect on a microring.

[0006] This application provides an all-optical intensity modulation device, which is entirely built on the same photonic integrated chip and entirely packaged in a sealed cavity filled with an absorbing gas; the all-optical intensity modulation device includes: an optical coupler, a micro-ring resonator, and a filter; An optical coupler is used to combine the signal light and the pump light and guide them together to the input coupling end of the microring resonator. The wavelength of the pump light is matched with the characteristic absorption peak wavelength of the absorbing gas, and the wavelength of the signal light is matched with the resonant wavelength of the microring resonator. A microring resonator is used to enhance the power of the pump light. The output intensity of the signal light is modulated by the change in the position of the resonance peak to obtain the modulated signal light. The modulated signal light is then output through the output coupling terminal. The change in the position of the resonance peak is caused by the heat energy generated by the absorption gas after the pump light is enhanced. A filter is used to remove residual pump light from the modulated signal light, so as to obtain pure modulated signal light.

[0007] Furthermore, the wavelength of the signal light is set in the linear region of the falling or rising edge of the microring resonance peak.

[0008] Furthermore, the absorbent gases include acetylene, methane, and carbon dioxide.

[0009] Furthermore, the microring resonator has a ring-shaped microcavity structure. The microring resonator can be a silicon nitride microring resonator, a silicon-based microring resonator, or a lithium niobate microring resonator, with a quality factor greater than or equal to 1 × 10⁻⁶. 3 .

[0010] Furthermore, the sealed cavity is constructed by depositing and patterning silicon nitride and silicon dioxide materials on the chip to form a sealed capping layer, and is pre-filled or replaced with absorbent gas through microfluidic channels.

[0011] Furthermore, it also includes: a signal light source, a pump light source, a first mode field coupler, and a second mode field coupler; Signal light source, used to generate the signal light to be modulated; Pump light source, used to generate pump light; The first mode field coupler is used to couple the signal light to the input waveguide of the chip; An optical coupler is specifically used to combine the signal light and the pump light in the input waveguide of the chip, and guide them together to the input coupling end of the microring resonator. The second mode field coupler is used to couple the clean, modulated signal light to the chip's output waveguide.

[0012] Furthermore, the all-optical intensity modulation device is realized monolithically using standard planar photonic integration technology.

[0013] Furthermore, the optical coupler can be a multimode interference coupler, a directional coupler, or a Y-coupler.

[0014] Furthermore, the first mode field coupler is an edge coupler, a micromirror coupler, a grating coupler, or an inverted conical coupler; the second mode field coupler is an edge coupler, a micromirror coupler, a grating coupler, or an inverted conical coupler.

[0015] Furthermore, the filter is a wavelength division multiplexer on the chip, with a transmittance of more than 50% for signal light and less than 1% for pump light.

[0016] Compared with the prior art, this application has the following advantages: 1. Compared with existing technical solutions, it is not necessary to introduce additional interference structures such as Mach-Zehnder interferometers (MZI) to complete the conversion from phase to intensity, which simplifies the device size and complexity.

[0017] 2. By coupling the pump light into the high-Q resonant mode of the microring, the intracavity optical power is enhanced by tens to hundreds of times. This design allows extremely low external pump light power (typically on the order of milliwatts or even lower) to be efficiently absorbed by the gas, generating a sufficiently significant temperature rise and refractive index change, thereby driving a significant shift in the microring's resonant peak. Compared to traditional solutions that require high-power pumping or rely on electric drive, this application has significant advantages in modulation efficiency and power consumption control.

[0018] 3. The entire modulation function, including the micro-ring resonator, coupler, and filtering, is implemented monolithically using standard planar photonic integration technology (such as CMOS-compatible technology) and packaged within a unified sealed gas chamber. This fully on-chip integration solution completely eliminates bulky, difficult-to-align fiber optic components or external gas chambers, making the device compact, stable, and suitable for large-scale on-chip integration.

[0019] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A schematic diagram of the structure of an on-chip all-optical intensity modulation device based on the gas photothermal effect on a microring, according to an embodiment of this application, is shown. Figure 2 The diagram shows the output signal of the on-chip all-optical intensity modulator according to an embodiment of this application under 100 kHz sinusoidal modulation of the pump light. Detailed Implementation

[0022] This application proposes an on-chip all-optical intensity modulation device based on the photothermal effect of gas on a microring. By combining the photothermal effect of gas with an on-chip microring resonator that is extremely sensitive to refractive index, the high-sensitivity shift in the resonant wavelength caused by the gas absorbing pump light is directly converted into a significant change in the signal light intensity within the passband, thus naturally converting refractive index modulation into intensity modulation. This not only achieves all-optical, low-power intensity modulation but also integrates a functional gas with a silicon-based photonic chip using standard on-chip integration technology. This solves the integration difficulties and limited functionality of existing solutions, providing a new path for developing high-performance, scalably integrated all-optical modulators.

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] like Figure 1 As shown, this is a schematic diagram of the structure of an on-chip all-optical intensity modulation device based on the photothermal effect of gas on a microring according to an embodiment of this application. The on-chip all-optical intensity modulation device is built on the same photonic integrated chip and is encapsulated in a sealed cavity filled with a specific absorbing gas. The on-chip all-optical intensity modulation device includes: a signal light source 1, a pump light source 2, a first mode field coupler 31, an optical coupler 4, a microring resonator 5, a filter 6, and a second mode field coupler 32. The signal light source 1 is used to generate the signal light to be modulated, specifically continuous signal light or pulsed signal light, and its operating wavelength (λ_s) is matched with the resonant wavelength of the micro-ring resonator 5. Specifically, the signal light can be preset to be near a certain resonant wavelength of the micro-ring resonator 5; The pump light source 2 is used to generate pump light, and the wavelength (λ_p) of the pump light needs to match the characteristic absorption peak wavelength of the specific absorbing gas (such as acetylene, methane, etc.) filled in the sealed cavity.

[0025] Specifically, the pump light source 2 is a semiconductor light source on a chip.

[0026] The first mode field coupler 31 is used to couple the signal light to the input waveguide of the chip; The optical coupler 4 is used to combine the signal light and the pump light and guide them together to the input coupling end of the microring resonator 5. The pump light source can be a single-wavelength light source or a light source of different wavelengths. When the light source is of different wavelengths, the optical coupler 4 is used to couple the pump light source of different wavelengths and the signal light coupled into the chip through the first mode field coupler device into different resonance modes of the micro-ring resonator.

[0027] The micro-ring resonator 5 is used to enhance the power of the pump light. It modulates the output intensity of the signal light by changing the position of the resonance peak and outputs the modulated signal light through the output coupling terminal. The change in the position of the resonance peak is caused by the heat energy generated by the absorption gas after the pump light is enhanced. The filter 6 is used to filter out residual pump light in the modulated signal light to obtain pure modulated signal light. The second mode field coupler 32 is used to couple the pure, modulated signal light to the output waveguide of the chip.

[0028] The optical coupler 4 can be a wavelength division multiplexing structure that is integrated on a chip and based on a directional coupler or an MMI coupler.

[0029] The microring resonator 5 is the core functional unit of the on-chip all-optical intensity modulation device. It is composed of a ring waveguide etched on the chip and has a high quality factor (Q value greater than or equal to 1 × 10⁻⁶). 3 ) and a specific free spectral range. The microring resonator 5 is placed in a hermetically sealed cavity integrated on a chip ( Figure 1 (Not separately indicated), it is typically formed by an airtight chamber structure covering the waveguide region of the microring resonator 5, filled with the aforementioned absorbing gas. Pump light (λ_p) is efficiently coupled into a resonant mode of the microring, and due to the resonance enhancement effect, its circulating optical power within the microring is greatly increased. The high power density pump light is strongly absorbed by gas molecules and rapidly converted into heat energy, causing a local temperature increase in the gas and the microring waveguide in close contact with it. This temperature change causes a change in the refractive index of the microring waveguide material (thermo-optic effect), resulting in a shift in the resonant spectrum of the microring resonator 5.

[0030] The key is that the wavelength of the signal light (λ_s) is precisely set at the edge of the microring resonant peak, for example, in the linear region of the falling or rising edge of the resonant peak. Therefore, when a change in pump light power causes a slight shift in the resonant peak, the transmittance of the signal light passing through the microring at that operating point changes drastically. In other words, the shift in the resonant peak is directly converted into a significant modulation of the signal light output intensity passing through the microring, achieving a complete optical conversion from pump light intensity to signal light intensity.

[0031] The modulated signal light is output from the micro-ring's output coupling terminal and enters filter 6. Filter 6 can be an integrated Bragg grating, wavelength division multiplexer, or other on-chip filter structure. Its function is to efficiently filter out residual pump light (λ_p), ensuring that the final output light contains only the modulated signal light. The pure modulated signal light is finally coupled to the output chip via the second mode field coupler 32, completing the entire modulation process.

[0032] Furthermore, the sealed cavity can be constructed by depositing and patterning materials such as silicon nitride and silicon dioxide on the chip to form a sealed capping layer, and pre-filled or replaced with an absorbent gas through a microfluidic channel. The geometric parameters (radius, waveguide cross-section) of the microring resonator 5 can be optimized according to the target modulation rate, power consumption, and modulation depth. In addition, the optical coupler 4 can also be designed to couple the pump light and signal light to different resonant modes of the microring resonator 5 respectively, to further optimize mode matching and modulation efficiency. The driving current of the pump light source 2 can be directly controlled by an external electrical signal, thereby realizing analog or digital modulation of the signal light intensity.

[0033] Specifically, the optical coupler is a multimode interference coupler, a directional coupler, or a Y-coupler.

[0034] Specifically, the first mode field coupler is an edge coupler, a micromirror coupler, a grating coupler, or an inverted conical coupler; the second mode field coupler is an edge coupler, a micromirror coupler, a grating coupler, or an inverted conical coupler.

[0035] Specifically, the filter is a wavelength division multiplexer or grating filter on a chip, with a transmittance of more than 50% for signal light and less than 1% for pump light.

[0036] like Figure 2As shown, in application, this scheme first controls the resonant modes of the temperature-controlled microring, aligning one of the resonant modes with the absorption line of acetylene gas. Then, the power of the pump light source is set to 2 mW, with the center wavelength aligned with the acetylene gas absorption line. In this implementation, the wavelength of the pump light is tuned by applying current, causing the pump light to sweep across the resonant modes of the microring. When the pump light sweeps across the resonant modes of the microring, it simultaneously aligns with the gas absorption line. At this point, the gas absorbs the enhanced pump laser energy and converts it into heat, causing the microring resonant peak to deviate. When the pump laser wavelength deviates from the microring's resonance, it also deviates from the gas's central absorption line. At this point, the gas absorbs almost no pump laser energy, and the microring's resonant mode returns to its initial state. In this implementation, the tuning frequency is 100 kHz, and it can be seen that the intensity of the signal light output after filtering exhibits the same frequency of intensity change. However, the intensity changes inconsistently every cycle. This is because the pump laser wavelength is sinusoidally tuned, sweeping back and forth across the microring resonance peak within the same cycle. The displacement length response of the microring resonance peak in the two wavelength directions is different (redshift / blueshift). By recording the output light intensity, it can be seen that a 2 mW pump laser can achieve high-frequency intensity modulation of the signal light exceeding 100 kHz.

[0037] like Figure 2 The embodiment shown applies current modulation to the pump light. In addition, the intensity modulation of the pump laser can be directly turned off, which can also achieve the modulation effect achieved in this application.

[0038] The core of this application lies in providing a highly integrated on-chip all-optical intensity modulation device. This device directly and efficiently converts the intensity variation of pump light into signal light intensity modulation through a combination of gas photothermal effect and micro-ring resonator, without the need for electrical intervention. The entire on-chip all-optical intensity modulation device is built on the same photonic integrated chip (such as a silicon-based or silicon nitride-based chip).

[0039] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A full-light intensity modulation device, characterized in that, The all-optical intensity modulation device is entirely built on the same photonic integrated chip and encapsulated in a sealed cavity filled with an absorbing gas; the all-optical intensity modulation device includes: an optical coupler, a micro-ring resonator, and a filter; The optical coupler is used to combine the signal light and the pump light and guide them together to the input coupling end of the microring resonator, wherein the wavelength of the pump light matches the characteristic absorption peak wavelength of the absorbing gas, and the wavelength of the signal light matches the resonant wavelength of the microring resonator. The microring resonator is used to enhance the power of the pump light. The output intensity of the signal light is modulated by the change in the position of the resonance peak to obtain the modulated signal light. The modulated signal light is then output through the output coupling terminal. The change in the position of the resonance peak is caused by the heat energy generated by the absorbed gas after the pump light is enhanced. The filter is used to remove residual pump light from the modulated signal light to obtain pure modulated signal light.

2. The all-optical intensity modulation device according to claim 1, characterized in that, The wavelength of the signal light is set in the linear region of the falling or rising edge of the microring resonance peak.

3. The all-optical intensity modulation device according to claim 1, characterized in that, The absorbent gases include acetylene, methane, and carbon dioxide.

4. The all-optical intensity modulation device according to any one of claims 1-3, characterized in that, The microring resonator has a ring-shaped microcavity structure, and is a silicon nitride microring resonator, a silicon-based microring resonator, or a lithium niobate microring resonator, with a quality factor greater than or equal to 1×10⁻⁶. 3 .

5. The all-optical intensity modulation device according to any one of claims 1-3, characterized in that, The sealed cavity is constructed by depositing and patterning silicon nitride and silicon dioxide materials on the chip to form a sealed capping layer, and is pre-filled or replaced with absorbent gas through microfluidic channels.

6. The all-optical intensity modulation device according to claim 1, characterized in that, Also includes: Signal light source, pump light source, first mode field coupler, and second mode field coupler; The signal light source is used to generate the signal light to be modulated; The pump light source is used to generate pump light; The first mode field coupler is used to couple the signal light to the input waveguide of the chip; The optical coupler is specifically used to combine the signal light and the pump light in the input waveguide of the chip, and guide them together to the input coupling end of the microring resonator. The second mode field coupler is used to couple the pure, modulated signal light to the output waveguide of the chip.

7. The all-optical intensity modulation device according to claim 6, characterized in that, The all-optical intensity modulation device is implemented on a single chip using standard planar photonic integration technology.

8. The all-optical intensity modulation device according to claim 1 or 6, characterized in that, The optical coupler is a multimode interference coupler, a directional coupler, or a Y-coupler.

9. The all-optical intensity modulation device according to claim 7, characterized in that, The first mode field coupler is an edge coupler, a micromirror coupler, a grating coupler, or an inverted conical coupler; the second mode field coupler is an edge coupler, a micromirror coupler, a grating coupler, or an inverted conical coupler.

10. The all-optical intensity modulation device according to claim 7, characterized in that, The filter is an on-chip wavelength division multiplexer with a transmittance of more than 50% for signal light and less than 1% for pump light.

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